The present invention relates to a head for a disk storage device.
In disk storage devices such as, for example, hard disks, the data is stored in tracks concentric with a rotation axis of the disk. A block of data is accessed (for reading or writing) by the positioning of an electromagnetic head mounted on a suspension arm adjacent the desired track.
A problem with disk storage devices is that, to ensure that they operate correctly, it is necessary for the head to be positioned extremely precisely within the track. Otherwise, the head may move over an adjacent track during a writing operation, destroying at least some of the data stored; similarly, during a reading operation, the head may detect incorrect data.
A known, dedicated solution for correcting the position of the head consists of the use of a servo-disk on which auxiliary positioning data (servo data) is recorded. A further servo-head fixed to the reading and writing head (or to a group of heads) reads the servo-data, enabling a servo-mechanism to keep all of the heads in the correct position within the track. This solution is extremely expensive since it requires the use of a suitable servo-disk and servo-head. Moreover, the control thus achieved is not very precise and is affected, in particular, by the different thermal expansion of the servo-head and of the servo-disk in comparison with the heads and the disks on which the useful data is stored.
A different, embedded solution is commonly used and consists in storing the auxiliary positioning servo-data on each track, intercalated with the useful data. In particular, each track is divided into various sectors, some of which are used for storing the positioning servo-data at regular intervals. When the disk is rotating, each head reads the auxiliary servo-data periodically, enabling the servo-mechanism to correct its position directly.
A disadvantage of this solution is that, during the movement of the head between two consecutive sectors containing servo-data, it is not possible to check and correct its position in any way; this structure does not therefore ensure the correct position of the head continuously. Moreover, the storage of the positioning servo-data on every track of the disk involves a considerable wastage, on the order of 10%, of the useful space on the disk.
The object of the present invention is to avoid the aforementioned drawbacks.
The head according to the present invention enables its position to be checked and corrected directly and continuously. This is particularly useful when the disk storage device is subject to knocks and vibrations as, for example, in portable devices.
This structure enables the head to follow the track extremely precisely; narrower tracks disposed closer together can thus be used, enabling storage devices with a greater data density to be produced.
The solution of the present invention does not require a dedicated device (a servo-disk or a servo-head) and is therefore extremely inexpensive. In addition, the present invention does not require the storage of any positioning servo-data, consequently avoiding wastage of space on the disk.
Further characteristics and advantages of the head according to the present invention will become clear from the following description of a preferred embodiment thereof, given by way of non-limiting example, with reference to the appended drawings.